{"id":21589,"date":"2024-01-02T11:59:23","date_gmt":"2024-01-02T11:59:23","guid":{"rendered":"https:\/\/server.hk\/blog\/21589\/"},"modified":"2024-11-14T10:30:12","modified_gmt":"2024-11-14T02:30:12","slug":"mongodb-glossary-accumulator","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/21589\/","title":{"rendered":"MongoDB \u8a5e\u5f59\u8868 &#8211; \u7d2f\u52a0\u5668"},"content":{"rendered":"<h1 id=\"mongodb-glossary-accumulator-xFZRKneSvb\">MongoDB \u8a5e\u5f59\u8868 &#8211; \u7d2f\u52a0\u5668<\/h1>\n<p>\u5728\u8cc7\u6599\u5eab\u7684\u4e16\u754c\u4e2d\uff0cMongoDB \u56e0\u5176\u9748\u6d3b\u6027\u548c\u53ef\u64f4\u5c55\u6027\u800c\u53d7\u5230\u5ee3\u6cdb\u6b61\u8fce\u3002\u4f5c\u70ba\u4e00\u7a2e NoSQL \u8cc7\u6599\u5eab\uff0cMongoDB \u63d0\u4f9b\u4e86\u5ee3\u6cdb\u7684\u529f\u80fd\uff0c\u4f7f\u5176\u6210\u70ba\u8a31\u591a\u958b\u767c\u4eba\u54e1\u548c\u4f01\u696d\u7684\u9996\u9078\u3002\u5176\u4e2d\u4e00\u9805\u91cd\u8981\u529f\u80fd\u662f\u7d2f\u52a0\u5668\uff0c\u5b83\u5728 MongoDB \u7684\u805a\u5408\u6846\u67b6\u4e2d\u767c\u63ee\u8457\u81f3\u95dc\u91cd\u8981\u7684\u4f5c\u7528\u3002<\/p>\n<h2 id=\"what-is-an-accumulator-xFZRKneSvb\">\u4ec0\u9ebc\u662f\u7d2f\u52a0\u5668\uff1f<\/h2>\n<p>\u5728 MongoDB \u4e2d\uff0c\u7d2f\u52a0\u5668\u662f\u4e00\u7a2e\u7528\u65bc\u805a\u5408\u7ba1\u9053\u4e2d\u7684\u904b\u7b97\u7b26\uff0c\u8ca0\u8cac\u5c0d\u4e00\u7d44\u6587\u4ef6\u57f7\u884c\u5404\u7a2e\u6578\u5b78\u904b\u7b97\u3002\u5b83\u63a5\u6536\u4e00\u500b\u8f38\u5165\u503c\uff0c\u4e26\u5c07\u5176\u8207\u5176\u4ed6\u503c\u9032\u884c\u7d2f\u52a0\uff0c\u4ee5\u7522\u751f\u55ae\u4e00\u7d50\u679c\u3002\u7d2f\u52a0\u5668\u4e3b\u8981\u7528\u65bc\u805a\u5408\u7ba1\u9053\u7684 <code>$group<\/code> \u968e\u6bb5\uff0c\u6839\u64da\u7279\u5b9a\u6a19\u6e96\u8a08\u7b97\u532f\u7e3d\u503c\u3002<\/p>\n<p>\u7d2f\u52a0\u5668\u53ef\u4ee5\u7528\u4f86\u57f7\u884c\u5404\u7a2e\u64cd\u4f5c\uff0c\u5305\u62ec\u6c42\u548c\u3001\u8a08\u7b97\u51fa\u73fe\u6b21\u6578\u3001\u627e\u51fa\u6700\u5927\u6216\u6700\u5c0f\u503c\u3001\u8a08\u7b97\u5e73\u5747\u503c\u7b49\u3002MongoDB \u63d0\u4f9b\u4e86\u4e00\u5957\u5167\u5efa\u7684\u7d2f\u52a0\u5668\uff0c\u80fd\u5920\u6709\u6548\u5730\u57f7\u884c\u9019\u4e9b\u64cd\u4f5c\u3002<\/p>\n<h2 id=\"common-accumulators-in-mongodb-xFZRKneSvb\">MongoDB \u5e38\u898b\u7684\u7d2f\u52a0\u5668<\/h2>\n<p>\u4ee5\u4e0b\u662f\u4e00\u4e9b\u5e38\u7528\u7684 MongoDB \u7d2f\u52a0\u5668\uff1a<\/p>\n<ul>\n<li><code>$sum<\/code>\uff1a\u8a08\u7b97\u7d44\u5167\u6578\u503c\u7684\u7e3d\u548c\u3002<\/li>\n<li><code>$avg<\/code>\uff1a\u8a08\u7b97\u7d44\u5167\u6578\u503c\u7684\u5e73\u5747\u503c\u3002<\/li>\n<li><code>$min<\/code>\uff1a\u627e\u51fa\u7d44\u5167\u7684\u6700\u5c0f\u503c\u3002<\/li>\n<li><code>$max<\/code>\uff1a\u627e\u51fa\u7d44\u5167\u7684\u6700\u5927\u503c\u3002<\/li>\n<li><code>$first<\/code>\uff1a\u8fd4\u56de\u7d44\u5167\u7684\u7b2c\u4e00\u500b\u503c\u3002<\/li>\n<li><code>$last<\/code>\uff1a\u8fd4\u56de\u7d44\u5167\u7684\u6700\u5f8c\u4e00\u500b\u503c\u3002<\/li>\n<li><code>$addToSet<\/code>\uff1a\u5c07\u552f\u4e00\u503c\u52a0\u5165\u6578\u7d44\u3002<\/li>\n<li><code>$push<\/code>\uff1a\u5c07\u503c\u52a0\u5165\u6578\u7d44\u3002<\/li>\n<li><code>$size<\/code>\uff1a\u8a08\u7b97\u6578\u7d44\u7684\u5927\u5c0f\u3002<\/li>\n<\/ul>\n<p>\u9019\u4e9b\u7d2f\u52a0\u5668\u53ef\u4ee5\u8207\u5176\u4ed6\u904b\u7b97\u7b26\u548c\u8868\u9054\u5f0f\u7d50\u5408\u4f7f\u7528\uff0c\u5f9e\u800c\u57f7\u884c\u8907\u96dc\u7684\u805a\u5408\u64cd\u4f5c\uff0c\u4e26\u5f9e\u8cc7\u6599\u4e2d\u751f\u6210\u6709\u50f9\u503c\u7684\u898b\u89e3\u3002<\/p>\n<h2 id=\"example-usage-xFZRKneSvb\">\u4f7f\u7528\u7bc4\u4f8b<\/h2>\n<p>\u5047\u8a2d\u6211\u5011\u6709\u4e00\u500b\u92b7\u552e\u8a02\u55ae\u7684\u96c6\u5408\uff0c\u4e26\u4e14\u6211\u5011\u5e0c\u671b\u8a08\u7b97\u6bcf\u500b\u7522\u54c1\u985e\u5225\u7684\u7e3d\u92b7\u552e\u984d\u3002\u6211\u5011\u53ef\u4ee5\u4f7f\u7528 <code>$group<\/code> \u968e\u6bb5\u548c <code>$sum<\/code> \u7d2f\u52a0\u5668\u4f86\u5be6\u73fe\u9019\u4e00\u76ee\u7684\uff1a<\/p>\n<pre><code>db.sales.aggregate([\r\n  {\r\n    $group: {\r\n      _id: \"$category\",\r\n      totalSales: { $sum: \"$amount\" }\r\n    }\r\n  }\r\n])\r\n<\/code><\/pre>\n<p>\u5728\u9019\u500b\u4f8b\u5b50\u4e2d\uff0c<code>$group<\/code> \u968e\u6bb5\u6309 &#8220;category&#8221; \u6b04\u4f4d\u5c0d\u6587\u4ef6\u9032\u884c\u5206\u7d44\uff0c\u4e26\u4f7f\u7528 <code>$sum<\/code> \u7d2f\u52a0\u5668\u8a08\u7b97\u6bcf\u500b\u985e\u5225\u7684 &#8220;amount&#8221; \u6b04\u4f4d\u7e3d\u548c\u3002\u7d50\u679c\u5c07\u662f\u985e\u5225\u53ca\u5176\u5404\u81ea\u7e3d\u92b7\u552e\u984d\u7684\u5217\u8868\u3002<\/p>\n<h2 id=\"conclusion-xFZRKneSvb\">\u7e3d\u7d50<\/h2>\n<p>\u7d2f\u52a0\u5668\u662f MongoDB \u805a\u5408\u6846\u67b6\u4e2d\u7684\u5f37\u5927\u5de5\u5177\uff0c\u5b83\u5141\u8a31\u60a8\u5c0d\u8cc7\u6599\u57f7\u884c\u5404\u7a2e\u6578\u5b78\u64cd\u4f5c\u3002\u901a\u904e\u5229\u7528\u7d2f\u52a0\u5668\uff0c\u60a8\u53ef\u4ee5\u5f9e MongoDB \u96c6\u5408\u4e2d\u7372\u5f97\u5bf6\u8cb4\u7684\u898b\u89e3\u4e26\u63d0\u53d6\u6709\u610f\u7fa9\u7684\u4fe1\u606f\u3002\u7121\u8ad6\u60a8\u9700\u8981\u8a08\u7b97\u7e3d\u548c\u3001\u5e73\u5747\u503c\uff0c\u9084\u662f\u5c0b\u627e\u6700\u5927\u503c\u6216\u6700\u5c0f\u503c\uff0c\u7d2f\u52a0\u5668\u90fd\u80fd\u63d0\u4f9b\u6eff\u8db3\u60a8\u7684\u805a\u5408\u9700\u6c42\u7684\u529f\u80fd\u3002<\/p>\n<p>\u6b32\u4e86\u89e3\u66f4\u591a\u6709\u95dc MongoDB \u53ca\u5176\u529f\u80fd\u7684\u8cc7\u8a0a\uff0c\u8acb\u8003\u616e\u700f\u89bd <a href=\"https:\/\/server.hk\">Server.HK<\/a>\uff0c\u9019\u662f\u4e00\u5bb6\u9818\u5148\u7684 VPS \u4e3b\u6a5f\u516c\u53f8\uff0c\u63d0\u4f9b\u53ef\u9760\u4e14\u53ef\u64f4\u5c55\u7684\u4e3b\u6a5f\u89e3\u6c7a\u65b9\u6848\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>MongoDB \u8a5e\u5f59\u8868 &#038;#82&#46;&#46;&#46;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4925],"tags":[],"class_list":["post-21589","post","type-post","status-publish","format-standard","hentry","category-4925"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/21589","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/comments?post=21589"}],"version-history":[{"count":2,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/21589\/revisions"}],"predecessor-version":[{"id":23852,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/21589\/revisions\/23852"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=21589"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=21589"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=21589"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}